In fabric dryers, notably of the type such as are used in commerical laundries, dyeing plants, etc., heated air is drawn through the dryer at a constant rate over the anticipated drying time at considerable volume. Commonly, the burner which heats the air is a two stage burner which operates initially at a high output level to bring the load and the dryer itself quickly up to an elevated temperature and when that temperature is sensed by a sensor in the exhaust system, drops to a lower output level for drying. The high stage may cycle on and off to keep the contents up to temperature and compensate for the evaporative cooling effect of the water in the wet load. The input of large quantities of heat together with large volumes of air results in a considerable wastage of heat or fuel during the early stages of the drying process when the load and dryer are being brought up to drying temperature which, of course, has the effect of extending the time of the drying cycle.